Nervous system – Normal
 Coronal section – opening slide
 Gray matter runs along edge (cortex), most of the rest is white matter
 Gray matter: at the very edge is where we actually do our thinking, neuronal cell bodies
 Wires: white matter, myelinated axons carrying information
 Computational devices: gray matter
 Connection: white matter
 Convolutions
 Maximize amount of area we have: have lots of convolutions to allow for more gray
matter
 Things that stick out: gyri (gyrus, singular)
 Ditches between them: sulci (sulcus, singular)
 General anatomy
 Longitudinal fissure: splits brain into right/left
 Cingulate gyrus: prominent anatomical landmark
 Corpus callosum: allows R and L sides to communicate
 Septum: “wall” between left & right lateral ventricles
 Caudate nucleus (along with globus pallidus & putamen): form the “striatum” [Latin:
stripe]
 caudate & globus pallidus are part of basal ganglia
 globus pallidus & putamen form the lenticular nucleus
 Insula: big convolution that allows us to have even more surface area
 Sylvian fissure forms the insula [Latin: island]
 Anterior commissure: another means to communicate L to R
 Amygdaloidal nucleus: almond shaped nucleus, fear center (if absent, person loses
inhibition) – usually just called “amygdala”
 Hippocampus: (next to amygdala – not shown in diagram) memory center (important that
fear and memory centers are very close together in order to stay alive – we really remember
danger so that we can avoid dangerous situations)
 Internal capsule: all information coming from cortex to body or vice versa goes through
here
 any damage to internal capsule will have tremendous adverse effects
 Corona radiata: sun’s rays; fibers span out in all directions from there
 Neurons
 Only place we find pseudounipolar cells is in sensory nerves
 Cell body and long dendrite and axon
 nerve in fingertip, dendrite all way up to dorsal root ganglia (DRG)
 axon from DRG to spinal cord and synapse immediately or travel to brain
 Multipolar cells make up 99.99% of neurons; lots of dendrites
 As things synapse, action potential at end causes depolarization & action potential
 At axon terminus, calcium comes in, releases neurotransmitter, binds on postsynaptic
cleft, something happens (either hyperpolarization: down or depolarization: up)
 Bipolar neurons are found in the eyes and ears.
 Axons can be myelinated (signal travels faster) or non-myelinated
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if supposed to be myelinated but loses it (it can no longer function; signal will travel
much slower or NOT at all)
Schwann cell in peripheral nervous system
Oligodendrocyte: Central Nervous system
 4 types of Glial cells: glue that holds brain together
 Astrocyte: wraps around capillary, the capillaries are completely covered by them, nothing
gets out of capillary without going through astrocyte, will then contact a neuron (form blood
brain barrier (BBB)) protect neurons from any potential harm that could reach neuron from
blood
 there are a lot of drugs that don’t work in brain because can’t cross the BBB
 Oligodendrocytes: myelate axons in the CNS
 Microglial cell: macrophage, samples the environment until it finds something wrong, then
becomes activated, causing an inflammatory response (activated by injury in brain; e.g. after
stroke or traumatic brain injury)
 Ependyma cells: line ventricles and ducts that CSF flows through
 have cilia in them that move CSF throughout
 in choroid plexus, ependyma cells create CSF
 Don’t worry about tanycytes (nobody else does)
 3 parts of brain:
 Cerebrum: 4 lobes of the cerebrum (named for their respective bones)
 Frontal
 Temporal
 Parietal
 Occipital
 Central sulcus: in front of it we have precentral gyrus, behind it the postcentral gyrus
 Lateral (or Sylvian) fissure separates frontal and temporal lobes
 Cerebellum
 Brainstem
 Midbrain
 Pons
 medulla oblongata
 Brodmann’s area
 Gray matter of cerebral cortex has 6 layers of cell types (e.g. input/output layers, processing
layers, communication layers, etc)
 Some parts of brain looked very different from others (structure determines function)
 Korbinian Brodmann Systematically mapped brain (published in 1909)
 Assumption: neighboring slices where brain had same structure would have same
function while neighboring areas that look different will have different function
 Don’t need to know Brodmann numbers but do need to know the names of areas on slide
 Some important parts of your brain
 Front of the brain: in front of central sulcus what you do to the world
 Back of the brain: what the world does to you
 Front of the brain
 Precentral gyrus: neurons of upper motor neuron (neuron that causes a muscle fiber to
contract)
 primary somatic motor areas
 Premotor cortex: where we coordinate muscles in order to move smoothly, getting the
sequence just right
 Frontal eye field: moving eyes, getting them to converge and focus, keeps movement of
eyes so in sync that we do not see double even when eyes are moving quickly
 Broca’s area: coordinating muscles of speech, very carefully time contraction and
relaxation of muscles – speech is extremely complicated muscle movements
 Prefrontal area: what makes you, you (least important part of your CNS; if you lost it you
would be boring and not do well on tests – but you could survive)
 Where we make plans, store declarative memories, etc.
 Personality & memories of your life, etc.
 Back of brain is sensory
 Postcentral gyrus: sensory equivalent of primary somatic motor, sensing an individual
sensory nerve ending
 primary somatic sensory cortex
 Visual cortex: approximately each pixel (rod or cone) has a neuron
 Auditory cortex: where we decode sounds – frequency decomposition of sound
 Association areas: putting things together
 Putting touch sensations together to feel things – somatic sensory association area
 Putting the pixels together to make pictures – visual association areas
 Putting sound components together to identify sounds – auditory association areas
 Angular gyrus: where we store information about things (what cat looks like, sounds like,
feels like)
 Angular gyrus is very close to the key language center (Wernicke’s area)
 Language probably started with just nouns (names of things)
 Homunculus: Describing motor and sensory cortex in visual way
 We don’t have equitable distribution of motor or sensory neurons across the body
 We want to distribute neurons to where we need more precision (toes v. fingers)
 would rather have motor neurons controlling fingers rather than toes or back
 likewise need more sensory neurons for hands, mouth/face, etc. than back
 Corticospinal tract = most important motor tract
 Starts in cortex, goes to spine  corticospinal
 Upper motor neuron: starts in motor cortex. Example, thumb control axon runs down
and decussates in medulla, continues down spine and synapses in spine (cervical
enlargement)
 lower motor neuron: starts in spinal cord. Example, thumb control runs from cervical
enlargement and down to innervate muscle (e.g. abductor pollicis brevis)
 (80-90%) cross over in medulla, rest decussate in anterior white commissure of spinal
cord, near the cell body of the lower motor neuron
 Both synapse in spine with the lower motor neuron runs
 Will not control head, face, larynx and pharynx (NOT controlled by spinal nerves, they are
controlled by cranial nerves)
 Corticobulbar tract (Bulb: think pons (bulb out of brainstem))
 Innervate the cranial nerves; upper motor neurons of lower motor neurons of cranial nerves
that control skeletal muscles
 1, 2, and 8 are the only cranial nerves that do NOT have motor components
 3, 4, 6 – ocular muscles
 5: Trigeminal: facial senses and mastication muscles
 7: Facial: facial expressions (muscle component)
 9: Glossopharyngeal: swallowing
 10: vagus: very many functions, skeletal muscles of pharynx & palate
 11: Accessory: sternocleidomastoid & trapezius
 12: Hypoglossal: tongue muscles
 Know all the functions of the cranial nerves on slide
 Rubrospinal & reticulospinal tracts
 Modulates the action of muscles (e.g. starting/stopping action)
 Parkinson’s: damage to substantia nigra normal strength but trouble initiating the action 
resting tremors
 DCML (Dorsal Column Medial Lemniscus): travel up dorsal columns of spinal cord (i.e.
fasciculus gracilis [legs] & fasciculus cuneatus [arms], cross at medulla, to medial lemniscus
continue up lemniscus  thalamus  primary sensory nucleus
 fine touch and kinesthesis
 stays on same side until it reaches the medulla oblongata
 Spinothalamic: spinal cord to thalamus
 pain and temperature
 immediately cross over in spinal cord, up to thalamus and then up to primary sensory cortex
 both pathways have cell bodies in dorsal root ganglia
 Pain synapses and crosses immediately at spinal cord (Spinothalamic)
 Large fiber impulses block pain and small fiber impulses increase pain
 by rubbing something when it hurts you activate large fiber impulses and it blocks the pain
 Brain can modulate sensitivity of our sensory pathways
 Spend a lot of time turning off sensory processes that are not important (sitting)
 Descending pathways from brain control sensitivity
 Narcotic drugs can also block pain channels
 Referred pain
 Pain in right side and right shoulder when you run
 Pain in side when running is always on right side
 Pain in shoulder when run always right shoulder
 the liver is complaining (liver refers pain to right side, and right shoulder)
 liver is moved up and down with diaphragm
 Heart: radiating down left arm, possibly up to neck
 Kidney pain: back and flanks
 Spinal cord
 7 cervical vertebrae but 8 cervical nerves
 12 thoracic
 5 lumbar
 5 sacral
 Spinal cord running through vertebral foramen
 Spinal cord part of CNS
 dura mater, arachnoid and pia mater
 neurons are myelinated by oligodendrocytes
 3 types of neurons enter/leave the spinal cord
 Somatic motor neurons
 Upper motor neuron synapses with lower motor neuron, lower motor neuron runs to
neuromuscular junction to innervate muscle
 Sensory neurons
 nerve ending, long dendrite, cell body and dorsal root ganglion, axon enter spinal cord
via dorsal horn
 Autonomic motor neurons
 axon that comes out of spinal cord, 1 synapse, postsynaptic neuron innervates end organ
 Dorsal (posterior): sensory
 Ventral (anterior): motor including motor autonomic (controls visceral functions)
 All nerves will contain both motor and sensory components
 reflex arc
 Hit patellar tendon: it gets dented in, lengthens muscle, signal goes back to interneuron to
say muscle lengthened, interneuron says generate more force to stop muscle from
lengthening
 When walking, at foot fall, knee is slightly bent
 Need to generate exact amount of force when walking, too little  fall, too much  hop
 Reflex arc allows us to generate exact amount of force to push against – without the
“brain” in the loop, this is much faster and off-loads processing from the brain
 Somatic v. autonomic motor neurons
 Somatic: spinal cord has lower motor neuron that runs to skeletal muscle, nothing between
except axon
 Autonomic: one synapse between spinal cord and end organ
 vagus innervating heart: neuron out of cardiorespiratory center, second neuron (post
synaptic neuron controls)
 slows heart down or decreases contractility
 One synapse between CNS and organ
 Exception: adrenal medulla (entire body is medulla’s post synaptic neuron) whole body
responds
 Acetylcholine: for all of the first axons, the neurotransmitter is acetylcholine
 For sympathetics the Second neuron transmitter is usually norepinephrine
 exception: sympathetic control of sweat glands uses acetylcholine at 2nd neuron
 For parasympathetics the second neuron transmitter is acetylcholine
 Autonomic nervous system
 Sympathetics
 Emerge from T1 - L2/3
 No sympathetics on cranial nerves
 parasympathetics
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on cranial nerves (3, 7, 9, 10)
No additional parasympathetics until we get down to sacral (usually S2 – S4)
 the vagus (10) controls everything below head and above descending colon
 sacral parasympathetics control distal colon, bladder and genitals
 Blood supply to brain & head
 Brachiocephalic (only on right side)
 R common carotid
 R subclavian
 L common carotid & L subclavian come directly off aorta
 Common carotid: split to internal and external carotid
 Vertebral arteries come off L & R subclavians
 Combine to form Basilar artery
 Enters skull through foramen magnum (big hole)
 Circle of Willis:
 Anterior, middle and posterior cerebral arteries
 Anterior and posterior communicating arteries
 left and right internal carotid
 Internal carotids give rise to L & R middle cerebral arteries
 Also gives rise to L & R anterior cerebral arteries
 basilar artery (two vertebrals came together)
 gives rise to L & R posterior cerebral arteries
 Have three ways to get blood to brain: if any one becomes blocked you still survive and
have proper functioning
 Anterior communicating artery connects L & R anterior cerebral arteries
 L & R posterior communication arteries connect posterior & middle cerebral arteries
 Often quite a bit of variation in distribution of blood flow
 Distribution of blood to the brain
 Anterior cerebral: coming off front of circle of Willis
 feeds medial frontal and medial parietal lobes
 Middle cerebral: comes out Sylvian fissure
 feeds lateral sections of brain (frontal, parietal, and temporal lobes)
 Posterior cerebral:
 Feeds occipital and lower temporal lobes
 Ventricles & CSF
 Lateral, 3rd and 4th ventricles
 We make cerebral spinal fluid in all but mostly in lateral ventricles
 Choroid plexus
 CSF flow
 Lateral ventricles  3rd ventricle  Cerebral aqueduct  4th ventricle
 From 4th ventricle: Two lateral foramina (Lushka), one medial foramen (Magendie)
 Circulates through brain in arachnoid region
 Numerous cisterns (large pools of CSF)
 reabsorbed by arachnoid granulation and dumped into superior sagittal sinus
 sinus is similar to vein, but made out of dura mater
 Central canal in spinal cord: usually obstructed (obstruction of no significance)
 CSF flow through arachnoid region
 CSF cushions the brain
 ~150 ml volume
 We make ~500 ml of CSF per day
 So we replace our CSF ~3 times per day
 Meninges
 Dura mater: tough leathery coating, adherent to skull
 Arachnoid mater: thin layer spider web like,
 CSF circulates through here
 Pia mater: layer closest to brain – adheres to brain